A new langbeinite-type phosphate K2GdHf(PO4)(3): synthesis, crystal structure, band structure and luminescence properties

摘要

Langbeinite-type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite-type compound, K2GdHf(PO4)(3) [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single-crystal X-ray diffraction. Theoretical studies reveal that K2GdHf(PO4)(3) is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O-2p -> Hf-5d transition. A Ce3+-doped phosphor, K2Gd0.99Ce0.01Hf(PO4)(3), was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d(1)-> 4f(1) transition of Ce3+. The average luminescence lifetime was calculated to be 5.437 ms and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K2Gd0.99Ce0.01Hf(PO4)(3) can be used as a good blue phosphor for three-colour white-light-emitting diodes (WLEDs).